Drill hammer-drill mechanism for power tool

ABSTRACT

A drill:hammer-drill arrangement is provided for a portable power tool wherein the hammering teeth are located immediately adjacent the chuck portion of the tool and wherein one set of hammering teeth are carried by the shaft which drives the chuck. A spring is provided which biases the chuck and the rotational hammer teeth forwardly relative to the tool during hammering while another spring biasses the stationary teeth toward the tool. In the hammer position, operator bias overcomes the spring force to engage the teeth and relative rotation causes hammering. In shifting into the drill position, a cam surface forces the chuck and the shaft on which the hammer teeth are mounted toward the tool until the shaft engages the forward bearing on the output spindle of the tool. Thus the forward bearing takes the thrust applied against the tool by the operator during drilling and eliminates the need for an independent thrust bearing.

United States Patent 91 Wood 1 [s 1 DRILL HAMMER-DRILL MECHANISM FORPOWER TOOL John W. Wood, Baltimore, Md.

Assignee: The Black and Decker Manufacturing Company, Towson, Md.

Filedz' June 7, 1971 Appl. No.: 150,339

Inventor:

U.S. Cl. ..173/48, 74/22 Int. Cl. ..B25d 11/10, E2lc l/l2 Field ofSearch l 73/48, 109; 74/22 References Cited UNITED STATES PATENTS 3/1969Bitter et a] ..74/22 M1964 Short ..173/4sx Primary EXaminerErnest R.Purser Attorney-Leonard Bloom, Joseph R. Slotnik and Edward D. Murphy I[451! May 1, 1973 [5 7] ABSTRACT A drillzhammer-drill arrangement isprovided for a portable power tool wherein the hammering teeth arelocated immediately adjacent the: chuck portion of the tool and whereinone set of hammering teeth are carried by the shaft which drives thechuck. A spring is provided which biases the chuck and the rotationalhammer teeth forwardly relative to the tool during hammering whileanother spring biasses the stationary teeth toward the tool. in thehammer position, operator bias overcomes the spring force to engage theteeth and relative rotation causes hammering. In shiftagainst the toolby the operator during drilling and eliminates the need for anindependent thrust bearing.

13 Claims, 3 Drawing Figures Patented May 1, 1973 3,730,281

DRILL HAMMER-DRILL MECHANISM FOR POWER TOOL The present invention isdirected to an improved power tool and specifically relates to animproved power drill which is capable of performing both drilling andhammer-drilling.

In the class of power tools such as drills which are commonly sold'tohomeowners and other light-duty users of such tools, there is a need fora tool which has a wide variety of capabilities so that the user doesnot need to purchase a separate tool for each of the various jobs he maywish to do. For example, while drilling operations are most commonlyperformed in wood or metal, the homeowner may occasionally wish to drillin more difficult materials such as concrete, brick, ceram ic tile, etc.Accordingly, it is desirable to provide a power drill which can beconverted easily from straight drilling to hammer-drilling on theseoccasions. However, since the need for this is relatively infrequent, itis also desirableto minimize the cost premium which the purchaser mustpay to obtain the hammer-drilling-option. It is therefore the purpose ofthis invention to provide a drill head for a power tool which is quicklyand easily convertible between drilling and hammerdrilling, which isimproved and simplified in construction and which is of less cost thanprevious units of this type.

Accordingly, it is an object of the present invention to provide a new,and improved construction for a drill:hammer-drill tool.

A further object of this invention is the provision of an inexpensivedrillzhammer-dril] device.

Another object of this invention is the provision of an improvedhammer-drill mechanism whichpermits increased impacting force at theoutput.

A further object of this invention is the provision of an improveddrilling thrust takeup in a drill:hammerdrill construction.

Further objects and advantages of this invention will become apparent asthe description and illustration thereof proceed.

Briefly, in accord with one embodiment of this invention, a drillzhammer-drill arrangement is provided for a portable power tool wherein thehammering teeth are located immediately adjacent the chuck portion ofthe tool and wherein one set of hammering teeth are carried by the shaftwhich drives the chuck. A spring is provided which biases the chuck andthe rotational hammer .teeth forwardly relative to the tool duringhammering while another spring biasses the stationary teeth toward thetool. In the hammer position, operator bias overcomes the spring forceto engage the teeth and relative rotation causes hammering. In shiftinginto the drill position, a cam surface forces the chuck and the shaft onwhich the hammer teeth are mounted toward the tool until the shaftengages the forward bearing on the output spindle of the tool. Thus theforward bearing takes the thrust applied against the tool by theoperator during drilling and eliminates the need for an independentthrust bearing. In the drawings:

FIG. I is a side elevation view of a power tool embodying the presentinvention;

FIG. 2 is a detailed view partially in cross section of the tool of FIG.I in a first operative position; and

FIG. 3 is a view similar to that: of FIG. 2 but showing the tool in asecond operative position.

In FIG. 1, a power tool 10 is illustrated which includes a housing 11covering, for example, an electric motor and a handle portion 12 whichincludes a cord set 13 for application of electric power to the motorand a trigger switch 14 for switching the tool on and off. A gear case15 is provided at the front end of the motor for converting the rotationof the electric motor to an appropriate speed to drive the chuck l6 andan output tool such as drill bit 17. Preferably, the chuck is attachedto the main bodyof thetool by an attachment coupling assembly such asthat described in my copending application Ser. No. 150,344, filed June7, 1971 which is assigned to the assignee of this invention. Asdescribed in that application, the attachment is engaged with the toolby inserting a bayonet member 18 on the attachment into a correspondingcoupling member 19 on the tool.

The specific subject matter of' the present invention is shown moreclearly in FIGS. 2 and 3. This mechanism is referred to hereinafter asan attachment, although it may be used either in the form of anattachment or in the form of a permanently mounted part of a tool. InFIG. 2, the drillzhammer-drill attachment 20 is illustrated in a firstposition wherein it is adapted for drilling only. In the context of theattachment coupling referred. toabove, this position may be defined byproviding a step 21 in the bayonet teeth 22 which are inserted into thecoupling member 19. Thus, upon inserting the attachment and rotating it,the step 21 engages with corresponding lugs 23 on the coupling memberand a lock button 24, carried by the coupling member 19, engages with aslot in the attachment, as is more completely described in myaforementioned application. l

The teeth 22 are carried on a coupling member 25 which is engaged with acarrier 26 of one set of hammer teeth 27 via spring 28. The couplingmember 25 extends radially inward to retain the carrier 29 of the otherset of hammer teeth 30. A stationary gripping ring 31 is also engagedwith the coupling member 25 so that the operator can grasp it to insertand rotate the teeth 22.

In my aforementioned application, the concept of spring biasing theattachment to the power unit is described. It is noted that the spring28 represents an alternative embodiment of this biasing. Specifically,when the teeth 22 or step portions 2l engage with the lugs 23 oncoupling member 19, the coupling member 25 is drawn toward the tool.Since this member is coupled to the attachment via spring .28, thespring force is exerted to draw the tool and the attachment into tighterengagement, in the manner described and claimed in that application.

Thus, the stationary part of the attachment includes gripping ring 31,coupling member 25 and carrier 26. These parts are engaged with thestationary outer members of the tool. The rotational portion of theattachment includes chuck 16 which is threaded on to a shaft 35. Inturn, the shaft 35 is adapted to be engaged with the output shaft 36extending from gear case 15.

- For example, the output shaft may include a cylindrical portion 37 forpiloting the chuck and a hexagonal por- 5 tion 38 for providing apositive drive coupling. The stationary and rotational parts of the toolare coupled via bearing 39 and, due to the improved piloting provided inthis arrangement, as described in my aforementioned application, nofurther bearing surface is required in the attachment portion.

The carrier 29 is press fitted on to the shaft 35 and rests against ashoulder 40 formed on the shaft. Thus, this carrier and the hammer teeth30 thereon are carried by and move with the shaft 35. In accord with thepresent invention, the drilling mode of operation is provided by movingthe entire attachment assembly inwardly into the coupling member 19until the leading end 41 of shaft 35 engages with inner race 42 ofbearing 39. In order to accomplish this movement, the step 21 in thecoupling teeth 22 is axially positionedso that engagement thereof withthe lugs 23 necessarily draws the shaft 35 into engagement with thebearing 39. Thus, in theposition illustrated in FIG. 2, operator thruston the tool is absorbed by the bearing 39. Since the shaft 35 cannotmove further into the tool, the hammer teeth 30 and 27 can never comeinto engagement and no hammering action will occur. The rotary motion ofthe output shaft 36 is transmitted to the chuck 16 and to any implementtherein such as bit 17 and the unit will function as a simple drill.

To produce hammering action, it is necessary to permit the teeth 27 and30 to come into engagement. In accordance with conventional hammer-drillconstruction, one set of teeth, 27, is stationary while the other set,30, rotates with the chuck. The leading edges of the sets of teeth arecammed so that, as the chuckand set 30 rotate, the main body of the toolis lifted a distance corresponding to the axial depth of the two sets ofteeth. As the set 30 continues to rotate, it moves out of engagementwith set 27, thus permitting the force of the operator pressure againstthe back of the tool to bang the tool forwardly, thus producing ahammering action on the work as the chuck rotates. Spring 43 is placedwithin the chuck to bias the chuck forwardly while spring 28 biases thestationary part into piloting engagement with the tool.

FIG. 3 illustrates the tool of this invention in a position wherehammering can occur. Specifically, the teeth 22 have been rotated sothat the step 21 has passed out of engagement with the lugs 23. As soonas the step moves beyond the lugs, the force of spring 43 moves theentire attachment forwardly with respect to the rest of the drill. Thus,shaft 35 moves away from bearing 39 and the hammer teeth set 30 is nowfree to move, either outwardly under the influence of spring 43 orinwardly when the operator overcomes this bias by pressing the toolagainst the work. To accommodate the relative movement of the hammerteeth 30, the hammer teeth 27 must also move outwardly so that they canbe engaged by hammer teeth 30 in the position of FIG. 3 and inwardly sothat they cannot be engaged thereby in the position of FIG. 2. Toaccomplish this movement, a set of stationary teeth 44 are provided atthe forward end of the tool and a corresponding set 45 is provided ontherearwardly facing surface of the carrier 26. Thus, as thedrillzhammer-drill device is rotated so that the step 21 moves out ofengagement with the coupling member- 19, the teeth 45 are also beingrotated to ride up on to teeth 44.

To summarize the operation of converting the tool from drilling tohammer-drilling, the lock button 24 is depressed to disengage it fromthe hammer-drill mechanism and then the gripping ring 31 is twistedrelative to the coupling member 19. The step 21 moves out of engagementwith the coupling member 19 and the spring 43 therefore draws themechanism away from the body of the tool by means of its pressureagainst the forward end of shaft 36. The shaft 35, carrier 29 and teeth30 are simply pulled forwardly by the spring 43 for a distancecorresponding to the height of step 21. At the same time, the stationaryteeth 44 and 45 ride on interacting cam surfaces so that the carrier 26is moved outwardly a distance corresponding to the movement of therotationary teeth 30 and carrier 29. When these motions have beencompleted, the lock button 24 engages another slot in the gripping ring31. Reverse rotation converts the tool back to the drilling mode.

Due to the movement of the hammer teeth sets as described, the end 41 ofshaft 35 is now spaced from the inner race 42 of bearing 39. Thus, whenthe operator presses the tool against an object to be drilled such as aconcrete block, etc., the chuck 16, the shaft 35, the carrier 29 and theteeth 30 can all be moved rearwardly against the force of spring 43 toengage the stationary teeth 27 and thus produce hammering action in themanner described above. At the same time, accurate piloting of thestationary portion of the attachment is maintained by the engagementbetween flat surfaces on teeth 44 and 45 and piloting of the rotationalportion of the attachment is maintained by the engagement of shaft 35with shaft 36.

The construction of a drillzhammer-drill mechanism as described above,embodies several advantages which are of particular importance. Forexample, the location of the hammer jaws at an extreme forward positionimmediately adjacent the chuck enables the full mass of the tool to beapplied to generate the hammering action. In addition, since the hammerjaws are located immediately adjacent the chuck rather than in the mainbody of the tool, the number of interfaces and other energy absorbersbetween the hammer. jaws and the work reduced, a larger quantity of theenergy contained in the shockwave generated at the hammer jaws isactually transmitted to the work. Another advantage of this constructionis that of taking up the thrust in the drilling mode on a bearing whichis required for rotational-to-stationary coupling, thus eliminating theneed for an independent thrust-take up member which would add to thecost and complexity of the unit. In the specific case of a power driverwith a variety of attachments, it is of particular advantage to providethe hammer mechanism in the attachment since this reduces the cost ofthe basic driver unit to those who have no need for the hammering actionwhile at the same time enabling this function to be readily available tothose who have need for it.

Accordingly, while a specific embodiment of this invention has beendescribed and illustrated, it will be clear to those skilled in the artthat many changes and modifications may be made from this embodimentwithout departing from the broader aspects of this invention.Accordingly, it is intended that the appended claims cover all suchchanges and modifications as fall within the true spirit and scope ofthis invention.

lclaim:

1. In a power drill having a motor, an output shaft driven by saidmotor, at least a forward bearing supporting said output shaft, and astationary bearing mount for said bearing; a mechanism arranged forconversion between the operations of drilling and hammermember engages arotating portion of said bearing and a second position wherein saiddrive member is spaced from said bearing, whereby in said firstposition, thrust applied between said tool and a workpiece is taken upby said bearing and in said second position, thrust applied between saidtool and a workpiece is effective to cause engagement of said sets ofhammer teeth.

2. Apparatus as claimed in claim 1 wherein said bearing comprises ananti-friction bearing having an inner race mounted on said output shaftand wherein said drive member in said first position engages said innerrace.

3. Apparatus as claimed in claim 2 wherein said bearing comprises a ballbearing, said ball bearing having an inner race mounted on said outputshaft.

4. Apparatus as claimed in claim 3 wherein said drive I member comprisesa sleeve mounted in torque-transmitting engagement with said outputshaft.

5. Apparatus as claimed in claim 1 wherein said means for moving saiddrive member comprises means biasing said mechanism away from saidoutput shaft.

6. Apparatus as claimed in claim 5 wherein said rotary hammer teeth areaffixed to and rotate with said drive member.

7. Apparatus as claimed in claim 6 wherein said means for moving saiddrive member further comprises second position, said stationary hammerteeth being moved axially forward along said output shaft; the movementof said drive member from said bearing mount to said second positionbeing sufficient to permit engagement of said rotary teeth with saidstationary teeth when thrust is applied between said tool and aworkpiece.

8. In a power drill having a motor, an output shaft driven by saidmotor, at least a forward bearing supporting said output shaft and astationary bearing output shaft between a first position wherein saiddrive mount for said bearing; a mechanism arranged for conversionbetween the operations of drilling and hammerdrilling comprising a drivemember for said drive mechanism, said drive member being slideablyengaged with said output shaft, a rotary set of hammer teeth mounted onsaid drive member; a stationary set of member enga es a rotating portionof said bearing and a second post ion wherein said drive member isspaced from said bearing, whereby in said first position, thrust appliedbetween said tool and a workpiece is taken up by said bearing and insaid second position, thrust applied between said tool and a workpieceis effective to cause engagement of said sets of hammer teeth; saidmeans for moving said drive member comprising means biasing saidmechanism away from said output shaft, at least one axially steppedtooth, each of said stepped surfaces being engageable with an opposedsurface to define a relative axial location therebetween, said opposedsurface being mounted on a stationary member retaining said bearing;said stepped tooth being positioned to cooperate with said means formoving said drive member so that engagement of one of said steppedsurfaces with said opposed surface permits movement of said drive memberto said first position and engagement of said other stepped surface withsaid opposed surface permits movement of said drive member to saidsecond position.

9. Apparatus as claimed in claim 8 wherein at least one of said hammerteeth sets :moves with said drive member.

10. Apparatus as claimed in claim 9 wherein said biasing means producesa force moving said drive member and said rotary hammer teeth away fromsaid motor and wherein further means are provided to move saidstationary hammer teeth away from said motor.

11. Apparatus as claimed in claim 10 wherein said bearing comprises ananti-friction bearing.

12. Apparatus as claimed in claim 11 wherein said mechanism furtherincludes locking means for retaining said mechanism in either of saidpositions.

13. An attachment for use with a power unit including a housing, a motorcontained within said housing, an output shaft extending from said motorand supported in a bearing, said bearing being mounted in said housing,said attachment being adapted for alternative- 1y performing drillingand hammer-drilling, said attachment comprising a plurality of steppedteeth arranged for engagement with said housing; a drive member fordriving engagement with said output shaft; a first set of rotary hammerteeth engaged with said drive member; a second set of stationary hammerteeth coupled to said stepped teeth; means for biasing said attachmentaway from said output shaft; one surface of said stepped teeth beingeffective, upon engagement with said housing, to overcome said biasingmeans to position said attachment in a first position close to saidtool, said drive member engaging a portion of said bearing in said firstposition to prevent engagement of said rotary and said stationary hammerteeth; and a second surface on said stepped teeth effective, uponengagement with said housing, to permit movement of said attachment awayfrom said tool to a second posi-

1. In a power drill having a motor, an output shaft driven by saidmotor, at least a forward bearing supporting said output shaft, and astationary bearing mount for said bearing; a mechanism arranged forconversion between the operations of drilling and hammer-drillingcomprising a drive member for said mechanism, said drive member beingslideably engaged with said output shaft; a rotary set of hammer teethmounted on said drive member; a stationary set of hammer teeth; saiddrive member extending rearwardly from said hammer teeth sets towardsaid bearing; and means for moving said drive member axially along saidoutput shaft between a first position wherein said drive member engagesa rotating portion of said bearing and a second position wherein saiddrive member is spaced from said bearing, whereby in said firstposition, thrust applied between said tool and a workpiece is taken upby said bearing and in said second position, thrust applied between saidtool and a workpiece is effective to cause engagement of said sets ofhammer teeth.
 2. Apparatus as claimed in claim 1 wherein said bearingcomprises an anti-friction bearing having an inner race mounted on saidoutput shaft and wherein said drive member in said first positionengages said inneR race.
 3. Apparatus as claimed in claim 2 wherein saidbearing comprises a ball bearing, said ball bearing having an inner racemounted on said output shaft.
 4. Apparatus as claimed in claim 3 whereinsaid drive member comprises a sleeve mounted in torque-transmittingengagement with said output shaft.
 5. Apparatus as claimed in claim 1wherein said means for moving said drive member comprises means biasingsaid mechanism away from said output shaft.
 6. Apparatus as claimed inclaim 5 wherein said rotary hammer teeth are affixed to and rotate withsaid drive member.
 7. Apparatus as claimed in claim 6 wherein said meansfor moving said drive member further comprises means for moving saidstationary hammer teeth axially of said output shaft, said means beingarranged so that in said first position, said stationary hammer teethare moved axially toward said motor, said rotary teeth being preventedfrom engagement with said stationary teeth by said bearing in said firstposition; and, in said second position, said stationary hammer teethbeing moved axially forward along said output shaft; the movement ofsaid drive member from said bearing mount to said second position beingsufficient to permit engagement of said rotary teeth with saidstationary teeth when thrust is applied between said tool and aworkpiece.
 8. In a power drill having a motor, an output shaft driven bysaid motor, at least a forward bearing supporting said output shaft anda stationary bearing mount for said bearing; a mechanism arranged forconversion between the operations of drilling and hammer-drillingcomprising a drive member for said drive mechanism, said drive memberbeing slideably engaged with said output shaft, a rotary set of hammerteeth mounted on said drive member; a stationary set of hammer teethcoupled to said bearing mount; and means for moving said drive memberaxially along said output shaft between a first position wherein saiddrive member engages a rotating portion of said bearing and a secondposition wherein said drive member is spaced from said bearing, wherebyin said first position, thrust applied between said tool and a workpieceis taken up by said bearing and in said second position, thrust appliedbetween said tool and a workpiece is effective to cause engagement ofsaid sets of hammer teeth; said means for moving said drive membercomprising means biasing said mechanism away from said output shaft, atleast one axially stepped tooth, each of said stepped surfaces beingengageable with an opposed surface to define a relative axial locationtherebetween, said opposed surface being mounted on a stationary memberretaining said bearing; said stepped tooth being positioned to cooperatewith said means for moving said drive member so that engagement of oneof said stepped surfaces with said opposed surface permits movement ofsaid drive member to said first position and engagement of said otherstepped surface with said opposed surface permits movement of said drivemember to said second position.
 9. Apparatus as claimed in claim 8wherein at least one of said hammer teeth sets moves with said drivemember.
 10. Apparatus as claimed in claim 9 wherein said biasing meansproduces a force moving said drive member and said rotary hammer teethaway from said motor and wherein further means are provided to move saidstationary hammer teeth away from said motor.
 11. Apparatus as claimedin claim 10 wherein said bearing comprises an anti-friction bearing. 12.Apparatus as claimed in claim 11 wherein said mechanism further includeslocking means for retaining said mechanism in either of said positions.13. An attachment for use with a power unit including a housing, a motorcontained within said housing, an output shaft extending from said motorand supported in a bearing, said bearing being mounted in said housing,said attachment being adapted for alternatively performing drilling andhammer-drilling, said attachment comprising a plurality of stepped teetHarranged for engagement with said housing; a drive member for drivingengagement with said output shaft; a first set of rotary hammer teethengaged with said drive member; a second set of stationary hammer teethcoupled to said stepped teeth; means for biasing said attachment awayfrom said output shaft; one surface of said stepped teeth beingeffective, upon engagement with said housing, to overcome said biasingmeans to position said attachment in a first position close to saidtool, said drive member engaging a portion of said bearing in said firstposition to prevent engagement of said rotary and said stationary hammerteeth; and a second surface on said stepped teeth effective, uponengagement with said housing, to permit movement of said attachment awayfrom said tool to a second position wherein said drive member is spacedfrom said bearing whereby engagement of said rotary and said stationaryhammer teeth is permitted.